1. Field of the Invention
The present invention relates to a telecommunication system. It is particularly, but not exclusively, concerned with a telecommunications system for mobile telephones.
2. Summary of the Prior Art
The present invention arises as a development of the ideas disclosed in WO 96/11557. A call to a mobile telephone is not to a fixed point, and therefore the system must determine the location of the destination. In arrangements prior to that disclosed in WO96/11557, a call to a mobile telephone results in a signal being transmitted to a data storage unit in the form of a Home Location Register unit (HLR) which determines the location of the mobile telephone, and so permits routing of the call to occur. Inevitably, HLRs have a limited capacity, and some arrangement is therefore necessary to enable telecommunication systems to access multiple HLRs. Therefore, WO96/11557 proposed that the switch network which connects users to other users, HLRs, and system services, had a register unit associated therewith, which register unit contained information relating each telephone number to a corresponding one of a plurality of HLRs. The relationship between telephone numbers and HLRs was then freely selectable within the register unit, so that the register unit acted as a converter between the number and the information identifying the HLR. By providing such a register unit, the fixed relationship between numbers and HLRs was broken, and any telephone number was then assignable to any HLR, assuming space permitted. Note that, although not explicitly mentioned in WO96/11557, it is not necessary that the different HLRs belong to a single service provider thus, it was possible for a user to have the same telephone number even when changing from one service provider to another.
WO96/11557 also mentioned that the register unit may also store further information associated with the mobile telephones which permitted the switch network to enable calls from mobile telephones to be routed to different services, depending on the calling mobile telephone itself, in addition to the number dialled.